U.S. patent application number 12/974023 was filed with the patent office on 2011-12-01 for organic light emitting diode display and method for compensating chromaticity coordinates thereof.
Invention is credited to Homin LIM.
Application Number | 20110292087 12/974023 |
Document ID | / |
Family ID | 45009463 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110292087 |
Kind Code |
A1 |
LIM; Homin |
December 1, 2011 |
ORGANIC LIGHT EMITTING DIODE DISPLAY AND METHOD FOR COMPENSATING
CHROMATICITY COORDINATES THEREOF
Abstract
An organic light emitting diode display, comprising: a display
panel on which a plurality of pixels are arranged, each of the
pixels comprising an R sub-pixel for generating red light through a
white OLED and an R color filter, a G sub-pixel for generating
green light through a white OLED and a G color filter, a B
sub-pixel for generating blue light through a white OLED and a B
color filter, and a W sub-pixel for generating white light through
a white OLED; a data operation unit for generating a data operation
value by extracting a representative value for each pixel based on
three primary color data, determining white data of the
corresponding pixel as the representative value, and then
subtracting the white data from the three primary color data for
each pixel; a gain adjusting unit for generating a gain adjusting
value of the three primary color data by multiplying a preset gain
value of the three primary color data by the corresponding white
data; and a data conversion unit for generating four color
compensation data, whose white chromaticity coordinates are
compensated for each pixel, by adding the gain adjusting value to
the data operation value and matching the corresponding white data
to the three primary color data converted by the adding.
Inventors: |
LIM; Homin; (Gyeonggi-do,
KR) |
Family ID: |
45009463 |
Appl. No.: |
12/974023 |
Filed: |
December 21, 2010 |
Current U.S.
Class: |
345/690 ;
345/76 |
Current CPC
Class: |
G09G 3/3225 20130101;
G09G 2300/0452 20130101; G09G 2340/06 20130101; G09G 2320/0666
20130101; G09G 2320/0242 20130101 |
Class at
Publication: |
345/690 ;
345/76 |
International
Class: |
G09G 5/10 20060101
G09G005/10; G09G 3/30 20060101 G09G003/30 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2010 |
KR |
10-2010-0049607 |
Claims
1. An organic light emitting diode display, comprising: a display
panel on which a plurality of pixels are arranged, each of the
pixels comprising an R sub-pixel for generating red light through a
white OLED and an R color filter, a G sub-pixel for generating
green light through a white OLED and a G color filter, a B
sub-pixel for generating blue light through a white OLED and a B
color filter, and a W sub-pixel for generating white light through
a white OLED; a data operation unit for generating a data operation
value by extracting a representative value for each pixel based on
three primary color data, determining white data of the
corresponding pixel as the representative value, and then
subtracting the white data from the three primary color data for
each pixel; a gain adjusting unit for generating a gain adjusting
value of the three primary color data by multiplying a preset gain
value of the three primary color data by the corresponding white
data; and a data conversion unit for generating four color
compensation data, whose white chromaticity coordinates are
compensated for each pixel, by adding the gain adjusting value to
the data operation value and matching the corresponding white data
to the three primary color data converted by the adding.
2. The organic light emitting diode display of claim 1, wherein the
gain adjusting unit generates a gain adjusting value for each gray
level or for each predetermined gray level interval with reference
to the gain value set for the gray level or for the gray level
intervals.
3. The organic light emitting diode display of claim 2, wherein the
gain value is defined as a value for converging white chromaticity
coordinates for each gray level or for each gray level interval to
a predetermined target value in accordance with the white data.
4. The organic light emitting diode display of claim 1, wherein the
representative value is extracted as the gray level value of
minimum data of the three primary color data.
5. The organic light emitting diode display of claim 1, wherein, in
a predetermined low gray level interval, the number of bits of the
gain value data becomes larger than the number of bits of
representable data.
6. The organic light emitting diode display of claim 5, wherein the
remaining bits of the white data after allocation to the low gray
level interval are additionally allocated to increase the gain
value in the low gray level interval.
7. The organic light emitting diode display of claim 1, further
comprising a first gain adjusting unit for primarily compensating
the white chromaticity coordinates of the three primary color data
by multiplying preset first gain values by the three primary color
data, and supplying the same to the data operation unit.
8. The organic light emitting diode display of claim 1, further
comprising a gamma conversion unit for gamma-converting the three
primary color data using a preset gamma curve and outputting the
same to the data operation unit, and for inverse-gamma-converting
and outputting the four color compensation data.
9. A method for compensating the chromaticity coordinates of an
organic light emitting diode display comprising a plurality of
pixels are arranged, each of the pixels comprising an R sub-pixel
for generating red light through a white OLED and an R color
filter, a G sub-pixel for generating green light through a white
OLED and a G color filter, a B sub-pixel for generating blue light
through a white OLED and a B color filter, and a W sub-pixel for
generating white light through a white OLED, the method comprising:
generating a data operation value by extracting a representative
value for each pixel based on three primary color data, determining
white data of the corresponding pixel as the representative value,
and then subtracting the white data from the three primary color
data for each pixel; generating a gain adjusting value of the three
primary color data by multiplying a preset gain value of the three
primary color data by the corresponding white data; and generating
four color compensation data, whose white chromaticity coordinates
are compensated for each pixel, by adding the gain adjusting value
to the data operation value and matching the corresponding white
data to the three primary color data converted by the adding.
10. The method of claim 9, wherein the gain adjusting unit
generates gain adjusting values for respective gray levels or for
respective preset gray level intervals with reference to the gain
values set for the respective gray levels or for the respective
gray level intervals.
11. The method of claim 10, wherein the gain values are defined as
values for converging the white chromaticity coordinates for each
gray level or for each gray level interval to predetermined target
values in accordance with the white data.
12. The method of claim 9, wherein the representative value is
extracted as the gray level value of minimum data of the three
primary color data.
13. The method of claim 9, wherein, in a predetermined low gray
level interval, the number of bits of the gain value data becomes
larger than the number of bits of representable data.
14. The method of claim 13, wherein the remaining bits of the white
data after allocation to the low gray level interval are
additionally allocated to increase the gain value in the low gray
level interval.
15. The method of claim 9, further comprising, prior to the
generating of the data operation value, primarily compensating the
white chromaticity coordinates of the three primary color data by
multiplying a preset first gain value by the three primary color
data, and supplying the same to the data operation unit.
16. The method of claim 9, further comprising, prior to the
generating of the data operation value, gamma-converting the three
primary color data using a preset gamma curve and outputting the
same to the data operation unit, and for inverse-gamma-converting
and outputting the four color compensation data.
Description
[0001] This application claims the benefit of Korea Patent
Application No. 10-2010-0049607 field on May 27, 2010, which is
incorporated herein by reference for all purposes as if fully set
forth herein.
BACKGROUND
[0002] 1. Field
[0003] This document relates to an organic light emitting diode
display and a method for compensating the chromaticity coordinates
thereof.
[0004] 2. Related Art
[0005] An active matrix type organic light emitting diode display
(AMOLED) is attracting a lot of attention as a next generation
display because of advantages of fast response speed, high light
emission efficiency, high luminance, and wide viewing angle. The
organic light emitting diode display displays an image by
controlling a current, flowing in an organic light emitting diode
(hereinafter, OLED) by using a thin film transistor (hereinafter,
referred to as "TFT").
[0006] A typical organic light emitting diode display has a
plurality of pixels, each comprising an R (red) sub-pixel, a G
(green) sub-pixel, and a B (blue) sub-pixel for full-color
displays. An R emission layer EML for generating red light is
formed in the OLED of the R sub-pixel, a G emission layer for
generating green light is formed in the OLED of the G sub-pixel,
and a B emission layer for generating blue light is formed in the
OLED of the B sub-pixel. An emission layer is deposited separately
for each sub-pixel by a fine metal mask (FMM) method using a metal
mask, etc. However, the larger the size of the substrate, the more
the mask is bent. Thus, the conventional deposition method using a
metal mask decreases yield because it makes it difficult to
precisely pattern an emission layer. As a result, it is hard to
apply this method to large area and high precision displays.
[0007] As such, in recent years, the technology of implementing a
color display device using a white OLED is emerging which does not
require the use of a metal mask during the formation of an emission
layer in an organic light emitting diode display. The white OLED
has a structure in which an R emission layer, a G emission layer, a
B emission layer, etc. are optionally laminated between a cathode
and an anode. The white OLED is formed for each sub-pixel. This
organic light emitting diode display has a plurality of pixels,
each comprising an R sub-pixel, a G sub-pixel, a B sub-pixel, and W
(white) sub-pixel for color displays. The R sub-pixel comprises an
R color filter for transmitting red light among white light
incident from the white OLED, the G sub-pixel comprises a G color
filter for transmitting green light among white light incident from
the white OLED, and a B color filter for transmitting blue light
among white light incident from the white OLED. The W sub-pixel has
no color filter, and transmits entire white light incident from the
white OLED to compensate for a decrease in image luminance caused
by the color filters.
[0008] Such an organic light emitting diode display generates W
data based on R data, G data, and B data input from the outside,
and modulates the R data, the G data, and the B data using the
generated W data. The W data, the modulated R data, the modulated G
data, and the modulated B data are respectively displayed in the W,
R, G, and B sub-pixels.
[0009] The aforementioned conventional art was proposed under the
assumption that the chromaticity coordinates of the white OLED are
uniform. However, in reality, the white OLED displays a white color
by a combination of emission layers of several colors. Thus, color
changes vary according to the driving voltage of the material used,
and this disturbs the color balance of white. This leads to a shift
in white chromaticity coordinates for each gray level when emitting
only W sub-pixels in the conventional art.
[0010] For example, in a panel where target values of the
chromaticity coordinates (x, y) are set to (0.290, 0.300), the
chromaticity coordinates (x, y) of a target luminance L for each
gray level are different from the target values (0.290, 0.300)
given in FIG. 1 due to the device characteristics of the white
OLED. In particular, the degree of a shift becomes larger toward
low gray levels as shown in FIG. 2, thus causing a yellowish
phenomenon in low gray levels. There is a demand for a method for
preventing the distribution of white chromaticity coordinates for
each gray level and converging them to predetermined target values,
as shown in FIG. 3, in an organic light emitting diode display
using a white OLED.
SUMMARY
[0011] The present invention has been made in an effort to provide
an organic light emitting diode display, which can compensate for
deviations in the characteristics of white chromaticity coordinates
for each gray level in the organic light emitting diode display
comprising a white OLED.
[0012] To achieve the above advantages, one exemplary embodiment of
the present invention provides an organic light emitting diode
display, comprising: a display panel on which a plurality of pixels
are arranged, each of the pixels comprising an R sub-pixel for
generating red light through a white OLED and an R color filter, a
G sub-pixel for generating green light through a white OLED and a G
color filter, a B sub-pixel for generating blue light through a
white OLED and a B color filter, and a W sub-pixel for generating
white light through a white OLED; a data operation unit for
generating a data operation value by extracting a representative
value for each pixel based on three primary color data, determining
white data of the corresponding pixel as the representative value,
and then subtracting the white data from the three primary color
data for each pixel; a gain adjusting unit for generating a gain
adjusting value of the three primary color data by multiplying a
preset gain value of the three primary color data by the
corresponding white data; and a data conversion unit for generating
four color compensation data, whose white chromaticity coordinates
are compensated for each pixel, by adding the gain adjusting value
to the data operation value and matching the corresponding white
data to the three primary color data converted by the adding.
[0013] The gain adjusting unit generates a gain adjusting value for
each gray level or for each predetermined gray level intervals with
reference to the gain value set for the gray level or for the gray
level interval.
[0014] The gain value is defined as a value for converging white
chromaticity coordinates for each gray level or for each gray level
interval to a predetermined target value in accordance with the
white data.
[0015] The representative value is extracted as the gray level
value of minimum data of the three primary color data.
[0016] In a predetermined low gray level interval, the number of
bits of the gain value data becomes larger than the number of bits
of representable data.
[0017] The remaining bits of the white data after allocation to the
low gray level interval are additionally allocated to increase the
gain value in the low gray level interval.
[0018] The organic light emitting diode display further comprises a
first gain adjusting unit for primarily compensating the white
chromaticity coordinates of the three primary color data by
multiplying a preset first gain value by the three primary color
data, and supplying the same to the data operation unit.
[0019] The organic light emitting diode display further comprises a
gamma conversion unit for gamma-converting the three primary color
data using a preset gamma curve and outputting the same to the data
operation unit, and for inverse-gamma-converting and outputting the
four color compensation data.
[0020] One exemplary embodiment of the present invention provides a
method for compensating the chromaticity coordinates of an organic
light emitting diode display comprising a plurality of pixels are
arranged, each of the pixels comprising an R sub-pixel for
generating red light through a white OLED and an R color filter, a
G sub-pixel for generating green light through a white OLED and a G
color filter, a B sub-pixel for generating blue light through a
white OLED and a B color filter, and a W sub-pixel for generating
white light through a white OLED, the method comprising: generating
a data operation value by extracting a representative value for
each pixel based on three primary color data, determining white
data of the corresponding pixel as the representative value, and
then subtracting the white data from the three primary color data
for each pixel; generating a gain adjusting value of the three
primary color data by multiplying a preset gain value of the three
primary color data by the corresponding white data; and generating
four color compensation data, whose white chromaticity coordinates
are compensated for each pixel, by adding the gain adjusting value
to the data operation value and matching the corresponding white
data to the three primary color data converted by the adding.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
[0022] In the drawings:
[0023] FIG. 1 is a view showing color characteristics for each gray
level of a white OLED device;
[0024] FIGS. 2 and 3 are views showing changes in the chromaticity
coordinates of the white OLED device;
[0025] FIG. 4 shows an organic light emitting diode display
according to an exemplary embodiment of the present invention;
[0026] FIG. 5 shows various array patterns of sub-pixels in one
pixel;
[0027] FIG. 6 shows a laminated configuration of sub-pixels in one
pixel;
[0028] FIG. 7 shows one example of the chromaticity coordinate
compensation circuit 14 of FIG. 6;
[0029] FIG. 8 shows one example of gain values for each gray level
of three primary data for compensating chromaticity coordinates for
each gray level;
[0030] FIGS. 9 to 11 show the result of adjusting chromaticity
coordinates for each gray level by applying the gain values of FIG.
8;
[0031] FIG. 12 shows another example of gain values for each gray
level of three primary color data for compensating chromaticity
coordinates for each gray level;
[0032] FIGS. 13 to 15 are views showing the result of adjusting
chromaticity coordinates for each gray level by applying the gain
values of FIG. 12; and
[0033] FIG. 16 is a view showing another example of the
chromaticity coordinate compensation circuit of FIG. 6.
DETAILED DESCRIPTION
[0034] Hereinafter, an implementation of this document will be
described in detail with reference to FIGS. 4 to 16.
[0035] FIG. 4 shows an organic light emitting diode display
according to an exemplary embodiment of the present invention. FIG.
5 shows various array patterns of sub-pixels in one pixel, and FIG.
6 shows a laminated configuration of sub-pixels in one pixel.
[0036] Referring to FIGS. 4 to 6, this organic light emitting diode
display comprises a display panel 10, a timing controller 11, a
data drive circuit 12, a gate drive circuit 13, and a chromaticity
coordinate compensation circuit 14.
[0037] In the display panel 10, a plurality of data lines 15 and a
plurality of gate lines 16 cross each other, and pixels P each
comprising four sub-pixels SPr, SPg, SPb, and SPw are arranged in
pixel areas defined by the crossings thereof. A pixel P comprises
an R sub-pixel SPr for generating R (red) light, a G sub-pixel SPg
for generating G (green) light, a B sub-pixel SPb for generating B
(blue) light, and a W sub-pixel SPw for generating W (white) light
for full color displays. The sub-pixels in one pixel P may form a
checkerboard pattern by the crossings of two data lines and two
gate lines as shown in (A) of FIG. 5, and may form a stripe pattern
by the crossings of four data lines and one gate line as shown in
(B) of FIG. 5. Moreover, the sub-pixels in one pixel P may form a
checkerboard pattern by the crossings of two data lines and two
gate lines as shown in (C) of FIG. 5, and the sub-pixels SPr and
SPg of an upper row and the sub-pixels SPb and SPw of a lower row
may be arranged so as to deviate from each other.
[0038] Each of the sub-pixels SPr, SPg, SPb, and SPw comprises a
white OLED which does not require the use of a metal mask during
the formation of an emission layer. The white OLED has a structure
in which an R emission layer, a G emission layer, a B emission
layer, etc. are optionally laminated between a cathode and an
anode. The white OLED is formed for each sub-pixel. As shown in
FIG. 6, the R sub-pixel SPr comprises an R color filter RCF for
transmitting red light among white light incident from the white
OLED, the G sub-pixel SPg comprises a G color filter GCF for
transmitting green light among white light incident from the white
OLED, and the B sub-pixel SPb comprises a B color filter BCF for
transmitting blue light among white light incident from the white
OLED. The W sub-pixel has no color filter, and transmits entire
white light incident from the white OLED to compensate for a
decrease in image luminance caused by the color filters RCF, GCF,
and BCF. In FIG. 6, `E1` may be an anode (or cathode), and `E` may
be a cathode (or anode). `E1` is electrically connected to a
driving TFT formed on a lower TFT array for each sub-pixel. Each
sub-pixel of the TFT array comprises a driving TFT, at least one
switching TFT, and a storage capacitor, and each sub-pixel is
connected to the data lines 15 and the gate lines 16.
[0039] The data driver 12 converts four color compensation data
RoGoBoWo whose chromaticity coordinates are compensated, into an
analog data voltage, and supplies it to the data lines 15 under the
control of the timing controller 11.
[0040] The gate driver 13 selects a horizontal line to which a data
voltage is applied by generating a scan pulse and sequentially
supplying it to the gate lines 16 under the control of the timing
controller 11.
[0041] The timing controller 11 generates a data control signal DDC
for controlling the operation timing of the data drive circuit 12
and a gate control signal GDC for controlling the operation timing
of the gate drive circuit 13 based on timing signals such as a
vertical synchronization signal Vsync, a horizontal synchronization
signal Hsync, a dot clock signal DCLK, and a data enable signal
DE.
[0042] The timing controller 11 supplies three primary color
digital video data RiGiBi input from the outside to the
chromaticity coordinate compensation circuit 14, and aligns four
color compensation data RoGoBoWo, whose chromaticity coordinates
are compensated, from the chromaticity coordinate compensation
circuit 14 according to the resolution of the display panel 10 and
then supplies it to the data drive circuit 12.
[0043] The chromaticity coordinate compensation circuit 14 converts
three primary color input digital video data RiGiBi into four color
digital video data RoGoBoWo, whose white chromaticity coordinates
are compensated in accordance with the characteristics of the white
OLEDs and color filters included in each of the pixels P, thereby
compensating for deviations in the characteristics of white
chromaticity coordinates for each gray level. The chromaticity
coordinate compensation circuit 14 may be incorporated in the
timing controller 11.
[0044] FIG. 7 shows one example of the chromaticity coordinate
compensation circuit 14 of FIG. 6. FIG. 8 shows one example of gain
values for each gray level of three primary data RiGiBi for
compensating chromaticity coordinates for each gray level. FIGS. 9
to 11 show the result of adjusting chromaticity coordinates for
each gray level by applying the gain values of FIG. 8. FIG. 12
shows another example of gain values for each gray level of three
primary color data RiGiBi data for compensating chromaticity
coordinates for each gray level. FIG. 13 shows the result of
adjusting chromaticity coordinates for each gray level by applying
the gain values of FIG. 12.
[0045] Referring to FIG. 7, the chromaticity coordinate
compensation circuit 14 comprises a first gamma conversion unit
141, a data operation unit 142, a gain adjusting unit 143, a data
conversion unit 144, and a second gamma conversion unit 145.
[0046] The first gamma conversion unit 141 receives three primary
color input data RiGiBi from a system board (not shown), and
gamma-converts the input data RiGiBi using any one of preset gamma
curves of 1.8 to 2 and then supplies it to the data operation unit
142.
[0047] The data operation unit 142 extracts a representative value
RV for each pixel based on the gamma-converted three primary color
data RiGiBi input from the data operation unit 142, determines
white data Wo of the corresponding pixel as the representative
value RV, and then subtracts the white data Wo from the
gamma-converted three primary color data RiGiBi for each pixel to
generate a data operation value Di-Wo (where Di indicates the
gamma-converted three primary color data RiGiBi). Then, the data
operation value Di-Wo and the white data Wo are output for each
pixel. To this end, the data operation unit 142 comprises a
representative value extractor 142A, a white data determiner 142B,
and a data operation value generator 142C.
[0048] The representative extractor 142A applies any one of known
algorithms, e.g., four algorithms Alg 1 to Alg. 4 shown in the
following Equation 1, to the gamma-converted three primary data
RiGiBi to extract a representative value RV for each pixel. In
Equation 1, `Yimin` indicates the gray level value of minimum data
among the gamma-converted three primary color data RiGiBi, and
`Yimax` indicates the gray level value of maximum data among the
gamma-converted three primary color data RiGiBi. In the application
of the first algorithm Alg. 1, the representative value RV for each
pixel is defined as `Yimin`. In the application of the second
algorithm Alg. 2, the representative value RV for each pixel is
defined as `Yimin2`. In the application of the third algorithm Alg.
3, the representative value RV for each pixel is defined as
`-Yimin3+Yimin2-Yimin`. In the application of the fourth algorithm
Alg. 4, if `Yimin/Yimax` is less than 0.5, the representative value
RV for each pixel is defined as `(Yimin*Yimax)/(Yimax-Yimin)`, and
if `Yimin/Yimax` is greater than 0.5, the representative value RV
for each pixel is defined as `Yimax`.
Alg . 1 : W o = Y i min Alg . 2 : W o = Y i min 2 Alg . 3 : W o = -
Y i min 3 + Y i min 2 + Y i min Alg . 4 : { W o = Y i min * Y i max
Y i max - Y i min if ( Y i min Y i max < 0.5 ) W o = Y i max if
( Y i min Y i max .gtoreq. 0.5 ) [ Equation 1 ] ##EQU00001##
[0049] Although the first to fourth algorithms Alg. 1 to Alg. 4 may
be optionally applied, the first algorithm is more desirable in
terms of algorithm size and minimization of a shift of the white
chromaticity coordinates. The following description of the
exemplary embodiment will be made with respect to the case where
the gray level value Yimin of minimum data of the gamma-converted
three primary color data RiGiBi is extracted as the representative
value RV for each pixel. The technical spirit of the present
invention is not limited to the four algorithms Alg. 1 to Alg. 4
exemplified in the above Equation 1. That is, the technical spirit
of the present invention is applicable to any known algorithm for
extracting the representative value.
[0050] The white data determiner 142B determines the white data Wo
of the corresponding pixel as the representative value RV, i.e.,
the gray level value of minimum data for each pixel, input from the
representative value extractor 142A.
[0051] The data operation value generator 142C generates the data
operation value Di-Wo by receiving the white data Wo from the white
data determiner 142B and subtracting the white data Wo from the
gamma-converted three primary color data RiGiBi for each pixel. The
data operation value Di-Wo comprises an R data operation value
Ri-Wo, a G data operation value Gi-Wo, and a B data operation value
Bi-Wo. The data operation value generator 142C outputs the data
operation value Di-Wo and the white data Wo for each pixel.
[0052] The gain adjusting unit 143 generates a gain adjusting value
of the three primary color data RiGiBi for each gray level (or for
each gray level interval) so that the white chromaticity
coordinates are not distributed for each gray level but converged
to predetermined target values when emitting white light in order
to adjust the chromaticity coordinates of a target luminance. To
this end, as shown in FIGS. 8 to 12, the gain adjusting unit 143
may refer to a lookup table storing the gain values G(Di) for
respective gray levels (or for respective gray level intervals) of
the three primary color data RiGiBi. The gain values G(Di) are
determined in advance by an experiment so that variations in white
chromaticity coordinates for each gray level in accordance with the
white data Wo are minimized, i.e., the white chromaticity
coordinates are converged to predetermined target values.
[0053] In one example, to correspond to the gain value G(Di) set
for each gray level interval of the three primary color data RiGiBi
as shown in FIG. 8, the gain adjusting unit 143 generates a gain
adjusting value Wo*G(Di) by multiplying the gain value G(Di) by the
white data Wo from the white data determiner 142B. The gain
adjusting value Wo*G(Di) comprises an R data gain adjusting value
Wo*G(R), a G data gain adjusting value Wo*G(G), and a B data gain
adjusting value Wo*G(B). By the gain adjusting value Wo*G(Di), the
chromaticity coordinates (x,y) of the target luminance L in every
gray level interval except a low gray level interval 0.about.31
Gray are converged near to predetermined target values (0.290,
0.300) as shown in FIG. 9. However, even if the maximum possible
gain value (e.g., `255` among gain value data consisting of 8 bits)
is applied in the low gray level interval 0.about.31 Gray,
convergence to the desired target values (0.290, 0.300) as shown in
FIGS. 9 to 11 do not occur.
[0054] To make up for this problem, it is necessary to increase the
gain value of low gray levels by extending the number of bits of
the gain value data in the low gray level interval 0.about.31 Gray.
Since the number of bits of white data Wo allocated to the low gray
level interval 0.about.31 Gray is less than 6 bits among the 8
bits, the remaining 2 bits may be additionally allocated to
increase the gain value of the low gray levels. FIG. 12 shows a low
gray level calibration gain value G(Di)*G(Lg) comprising a gain
value increment in the low gray level interval 0.about.31 Gray in
addition to the gain value G(Di) of FIG. 8. The gain value for the
low gray level interval 0.about.31 Gray may increase from `255` of
FIG. 8 to `484` of FIG. 12 by additional bit allocation. To
correspond to this, the gain adjusting unit 143 generates a
calibration gain adjusting value Wo*G(Di)*G(Lg) by multiplying the
calibration gain value G(Di)*G(Lg) by the white data Wo from the
white data determiner 1423. The calibration gain adjusting value
Wo*G(Di)*G(Lg) comprises an R data calibration gain adjusting value
Wo*G(R)*G(Lg), a G data calibration gain adjusting value
Wo*G(G)*G(Lg), and a B data calibration gain adjusting value
Wo*G(B)*G(Lg). By the calibration gain adjusting value
Wo*G(Di)*G(Lg), the chromaticity coordinates (x,y) of the target
luminance L in every gray level interval except the low gray level
interval 0.about.31 Gray are converged near to predetermined target
values (0.290, 0.300) as shown in FIGS. 13 to 15. The gain values
shown in FIGS. 8 to 12 may be set to different values as needed
depending on the panel condition.
[0055] The data conversion unit 144 adds the gain adjusting value
Wo*G(Di) (or the calibration gain adjusting value Wo*G(Di)*G(Lg)
from the gain adjusting unit 143) to the data operation value Di-Wo
from the data operation value generator 142C, and matches the
corresponding white data Wo to the three primary color data RoGoBo
converted by the adding, thereby generating four color compensation
data RoGoBoWo.
[0056] The second gamma conversion unit 145 inverse-gamma-converts
the four color compensation data RoGoBoWo input from the data
conversion unit 144.
[0057] FIG. 16 shows another example of the chromaticity coordinate
compensation circuit 14 of FIG. 6.
[0058] Referring to FIG. 16, the chromaticity coordinate
compensation circuit 14 comprises a first gamma conversion unit
241, a first gain adjusting unit 242, a data operation unit 243, a
second gain adjusting unit 244, a data conversion unit 245, and a
second gamma conversion unit 246.
[0059] The chromaticity coordinate compensation circuit 14 of FIG.
16 further comprises the first gain adjusting unit 242 unlike that
of FIG. 7.
[0060] The first gain adjusting unit 242 primarily compensates the
white chromaticity coordinates of the three primary color data
RiGiBi by multiplying a preset first gain value G1(Di) for each
gray level (or for each gray level interval) by the gamma-converted
three primary color data RiGiBi so that the white chromaticity
coordinates are not distributed for each gray level but converged
to predetermined target values when emitting white light in order
to adjust the chromaticity coordinates of a target luminance. To
this end, the first gain adjusting unit 242 may refer to a lookup
table storing the first gain values G1(Di) for respective gray
levels (or for respective gray level intervals) of the three
primary color data RiGiBi. The first gain values G1(Di) are
determined in advance by an experiment so that variations in white
chromaticity coordinates for each gray level in accordance with the
white data Wo are minimized, i.e., the white chromaticity
coordinates are converged to predetermined target values.
[0061] The first gamma conversion unit 241, data operation unit
243, second gain adjusting unit 244, data conversion unit 245, and
second gamma conversion unit 246 of FIG. 16 respectively correspond
to the first gamma conversion unit 141, data operation unit 142,
gain adjusting unit 143, data conversion unit 144, and second gamma
conversion unit 145 of FIG. 7. The functions and operations of the
corresponding components 241, 243, 244, 245, and 246 of FIG. 16 are
substantially identical to those as described above through FIGS. 7
to 15 except that three primary color data RiGiBi, multiplied by
the first gain value G1(Di), is input into the data operation unit
243 and a data operation value G1(Di)*Di-Wo, to which the first
gain value G1(Di) is applied, is input into the data conversion
unit 245.
[0062] As described above in detail, the organic light emitting
diode display and the method for compensating the chromaticity
coordinates thereof according to the present invention can greatly
improve picture quality by compensating for deviations in the
characteristics of white chromaticity coordinates for each gray
level in the organic light emitting diode display comprising a
white OLED
[0063] From the above description, it will be apparent to those
skilled in the art that various changes and modifications can be
made without departing from the technical spirit of the present
invention. Accordingly, the scope of the present invention should
not be limited by the exemplary embodiments, but should be defined
by the appended claims.
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